1. Field of the Invention
The present invention relates to an apparatus and method of synthesizing a spotlighted image.
2. Description of the Prior Art
Various types of image synthesizing systems are known which may be used in three-dimensional games, simulators for controlling airplanes and other vehicles and others. In such image synthesizing systems, image information relating to such a three-dimensional object 300 as shown in FIG. 13A has been stored therein. The three-dimensional object 300 represents a scenery or other expression which can be seen by a player (observer) 302 through a screen 306. The image information of the three-dimensional object 300 is perspectively transformed onto the screen 306 to form an image (projected image) 308. When the player 302 rotates or translates a moving body on which the player 302 is assumed to get through a control panel 304, the player 302 or the moving body will be changed in position and direction. Depending on such changes, a computation is performed relating to how manner the image of the three-dimensional object 300 is to be viewed on the screen 306 in. Such a computation will be made in real time following the control by the player 302. Thus, the player 302 can see a changed scenery or expression associated with the changed position and direction of the player or the moving body on which the player gets as a pseudo three-dimensional image in real time. This will make the player to experience a virtual reality in a virtual three-dimensional space.
FIG. 13B shows an image (game scene) which can be formed by such an image synthesizing system as described above.
It has been desired that the aforementioned image synthesizing systems have a spotlight display function of forming a more real image, for example, an image of a scene lighted up by headlights of a car.
One of various techniques for accomplishing such a spotlight display is shown in FIG. 14. Such a technique uses a mixing unit 504 for mixing a two-dimensional image 506 from a three-dimensional image synthesizing unit 500 with a headlight pattern (two-dimensional image) 508 which is a translucent pattern or brightness processing pattern from a headlight pattern generating unit 502 (to obtain a superimposed image or to change brightness) to form an output image 510. In such a case, the two-dimensional image 506 from the three-dimensional image synthesizing unit 500 has already been subjected to shading and depth cueing computation after the perspective transformation. The headlight pattern 508 from the headlight pattern generating unit 502 is a translucent pattern or brightness processing pattern so that the two-dimensional image 506 can be seen. The headlight pattern is further designed such that the pattern part intended to be on the optical axis of the headlight is more bright and the marginal part of the headlight is more dark in a direction apart from the optical axis.
However, such a technique has the following disadvantages. It is now assumed that a car which is radiating headlight beams is turned laterally against a wall by the side of a road due to any cause. Since the car is designed to move freely in a virtual three-dimensional space, it is naturally considered that such an event occurs. The headlight pattern 508 is intended to be most real when the car runs straight along a road. When the headlight beams are projected against the wall as described, however, a problem may be raised in that the headlight pattern is formed in a configuration far away from the reality. This is because the mixing unit 504 superimposes two images without their depth information.
In order to display the headlight with more reality, two light sources may be set in the headlight portion of the car. The shading computation may be then carried out based on the two light sources. However, since the two light sources cannot be considered to be at the infinite points in such a case, the light beams from the light sources cannot be made as parallel rays. Thus, the shading operation based on these light sources will require a huge computation, resulting in being more complicated. This is an obstruction on increasing the operational speed of the image synthesizing system and also on lowering the manufacturing cost of the same.
The present invention is directed to overcome the aforementioned technical problems. An object of the present invention is therefore to provide an image synthesizing system and method which can attain a spotlight display reflecting the depth information with high speed image synthesizing and low cost manufacturing.